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Message-ID: <zxcvscosad6yv2y6km3xsdhh26qse3qcx5u66a4nqybev4u64y@uzdekpsliv35>
Date: Fri, 30 May 2025 18:00:15 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: George Hu <integral@...hlinux.org>
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bcachefs: use union for bch_compression_opt to make
encode & decode easier
On Fri, May 30, 2025 at 10:52:43PM +0800, George Hu wrote:
> Eliminate redundant encode & decode function by using union for
> bch_compression_opt, which reduces code complexity.
order of bitfield members is not fixed, to do this you need #ifdef
__LITTLE_ENDIN_BITFIELD...
>
> Signed-off-by: George Hu <integral@...hlinux.org>
> ---
> fs/bcachefs/compress.c | 17 +++++++++--------
> fs/bcachefs/compress.h | 32 +++++++-------------------------
> fs/bcachefs/extents.c | 2 +-
> 3 files changed, 17 insertions(+), 34 deletions(-)
>
> diff --git a/fs/bcachefs/compress.c b/fs/bcachefs/compress.c
> index 1bca61d17092..10e88e14f5ed 100644
> --- a/fs/bcachefs/compress.c
> +++ b/fs/bcachefs/compress.c
> @@ -336,7 +336,7 @@ static int attempt_compress(struct bch_fs *c,
> void *workspace,
> void *dst, size_t dst_len,
> void *src, size_t src_len,
> - struct bch_compression_opt compression)
> + union bch_compression_opt compression)
> {
> enum bch_compression_type compression_type =
> __bch2_compression_opt_to_type[compression.type];
> @@ -426,7 +426,7 @@ static int attempt_compress(struct bch_fs *c,
> static unsigned __bio_compress(struct bch_fs *c,
> struct bio *dst, size_t *dst_len,
> struct bio *src, size_t *src_len,
> - struct bch_compression_opt compression)
> + union bch_compression_opt compression)
> {
> struct bbuf src_data = { NULL }, dst_data = { NULL };
> void *workspace;
> @@ -553,7 +553,7 @@ unsigned bch2_bio_compress(struct bch_fs *c,
>
> compression_type =
> __bio_compress(c, dst, dst_len, src, src_len,
> - bch2_compression_decode(compression_opt));
> + (union bch_compression_opt){ .value = compression_opt });
>
> dst->bi_iter.bi_size = orig_dst;
> src->bi_iter.bi_size = orig_src;
> @@ -602,7 +602,8 @@ static int __bch2_check_set_has_compressed_data(struct bch_fs *c, u64 f)
> int bch2_check_set_has_compressed_data(struct bch_fs *c,
> unsigned compression_opt)
> {
> - unsigned compression_type = bch2_compression_decode(compression_opt).type;
> + unsigned int compression_type = ((union bch_compression_opt){ .value = compression_opt })
> + .type;
>
> BUG_ON(compression_type >= ARRAY_SIZE(bch2_compression_opt_to_feature));
>
> @@ -683,7 +684,7 @@ static int __bch2_fs_compress_init(struct bch_fs *c, u64 features)
>
> static u64 compression_opt_to_feature(unsigned v)
> {
> - unsigned type = bch2_compression_decode(v).type;
> + unsigned int type = ((union bch_compression_opt){ .value = v }).type;
>
> return BIT_ULL(bch2_compression_opt_to_feature[type]);
> }
> @@ -703,7 +704,7 @@ int bch2_opt_compression_parse(struct bch_fs *c, const char *_val, u64 *res,
> {
> char *val = kstrdup(_val, GFP_KERNEL);
> char *p = val, *type_str, *level_str;
> - struct bch_compression_opt opt = { 0 };
> + union bch_compression_opt opt = { 0 };
> int ret;
>
> if (!val)
> @@ -736,7 +737,7 @@ int bch2_opt_compression_parse(struct bch_fs *c, const char *_val, u64 *res,
> opt.level = level;
> }
>
> - *res = bch2_compression_encode(opt);
> + *res = opt.value;
> err:
> kfree(val);
> return ret;
> @@ -744,7 +745,7 @@ int bch2_opt_compression_parse(struct bch_fs *c, const char *_val, u64 *res,
>
> void bch2_compression_opt_to_text(struct printbuf *out, u64 v)
> {
> - struct bch_compression_opt opt = bch2_compression_decode(v);
> + union bch_compression_opt opt = { .value = v };
>
> if (opt.type < BCH_COMPRESSION_OPT_NR)
> prt_str(out, bch2_compression_opts[opt.type]);
> diff --git a/fs/bcachefs/compress.h b/fs/bcachefs/compress.h
> index bec2f05bfd52..8cded510b2ac 100644
> --- a/fs/bcachefs/compress.h
> +++ b/fs/bcachefs/compress.h
> @@ -10,41 +10,23 @@ static const unsigned __bch2_compression_opt_to_type[] = {
> #undef x
> };
>
> -struct bch_compression_opt {
> - u8 type:4,
> - level:4;
> -};
> -
> -static inline struct bch_compression_opt __bch2_compression_decode(unsigned v)
> -{
> - return (struct bch_compression_opt) {
> - .type = v & 15,
> - .level = v >> 4,
> +union bch_compression_opt {
> + u8 value;
> + struct {
> + u8 type:4, level:4;
> };
> -}
> +};
>
> static inline bool bch2_compression_opt_valid(unsigned v)
> {
> - struct bch_compression_opt opt = __bch2_compression_decode(v);
> + union bch_compression_opt opt = { .value = v };
>
> return opt.type < ARRAY_SIZE(__bch2_compression_opt_to_type) && !(!opt.type && opt.level);
> }
>
> -static inline struct bch_compression_opt bch2_compression_decode(unsigned v)
> -{
> - return bch2_compression_opt_valid(v)
> - ? __bch2_compression_decode(v)
> - : (struct bch_compression_opt) { 0 };
> -}
> -
> -static inline unsigned bch2_compression_encode(struct bch_compression_opt opt)
> -{
> - return opt.type|(opt.level << 4);
> -}
> -
> static inline enum bch_compression_type bch2_compression_opt_to_type(unsigned v)
> {
> - return __bch2_compression_opt_to_type[bch2_compression_decode(v).type];
> + return __bch2_compression_opt_to_type[((union bch_compression_opt){ .value = v }).type];
> }
>
> struct bch_write_op;
> diff --git a/fs/bcachefs/extents.c b/fs/bcachefs/extents.c
> index 677cf453b332..64419c028662 100644
> --- a/fs/bcachefs/extents.c
> +++ b/fs/bcachefs/extents.c
> @@ -1512,7 +1512,7 @@ int bch2_bkey_ptrs_validate(struct bch_fs *c, struct bkey_s_c k,
> const struct bch_extent_rebalance *r = &entry->rebalance;
>
> if (!bch2_compression_opt_valid(r->compression)) {
> - struct bch_compression_opt opt = __bch2_compression_decode(r->compression);
> + union bch_compression_opt opt = { .value = r->compression };
> prt_printf(err, "invalid compression opt %u:%u",
> opt.type, opt.level);
> return -BCH_ERR_invalid_bkey;
> --
> 2.49.0
>
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